The subject matter of the following copending patent applications being filed on even date herewith is closely related to the subject matter of the present application and is incorporated herein by reference to the extent it is not incompatible with the present disclosure: APPARATUS AND METHOD FOR POSITIONING A BIOPSY NEEDLE (Ser. No. 08/722,725), APPARATUS AND METHOD FOR AUTOMATICALLY POSITIONING A BIOPSY NEEDLE (Ser. No. 08/722,707), and TRIGONOMETRIC DEPTH GAUGE FOR BIOPSY NEEDLE (Ser. No. 08/722,724, now abandoned). All are filed in the names of Navab and Geiger, the present inventors, and all are assigned to Siemens Corporate Research, Inc., as is the present application.
Needle biopsy is one of the most frequent surgical interventions. Typically, a fine needle is used to remove tissue portions from a lesion inside the body. If the lesion is very small and is deep-seated within the body or is not palpable, the surgeon needs guidance in order to make sure that the tip of the needle reaches the desired location.
Currently used image based guidance methods include the following. Ultrasound (US), X-ray fluoroscopy, computerized tomography (CT) fluoroscopy and computerized tomography/magnetic resonance imaging (CT/MRI) in combination with real time registration tools. The first three methods provide real time intra-operative images of the patient and enable the surgeon to see the needle as it approaches the target.
Ultrasound is relatively inexpensive and is a readily available image modality. However, its usage for guidance is limited to lesions that are close to the skin and that show a well defined signal.
The X-ray fluoroscope is a widely available, low cost two-dimensional (2D) imaging equipment. Since it shows a two-dimensional projection, two (generally orthogonal) views are necessary in order to determine the biopsy needle position. This can be done by turning the arm of a simple fluoroscope, such as a C-arm fluoroscope, an example of which is shown in FIG. 1, or by using a fluoroscope such as that illustrated in FIG. 2 that provides two simultaneous orthogonal views. Since the needle has to be manipulated in the image field, one cannot avoid a X-ray exposure of the physician when using such techniques. As is well-known, unnecessary exposure of health workers to X-ray radiation is believed to be hazardous to health and it is desirable that it should be avoided to the extent possible.
CT-Fluoroscopy permits real-time display of CT images. The physician controls X-ray exposure during continuous tube rotation. The exact position of the needle can be traced by moving the table. In the case for CT-Fluoroscopy also, the surgeon is exposed to X-rays.
CT/MRI in combination with real time registration tools is based on pre-operative 3-D data acquisition (CT or MRI). The lesion is outlined in the resulting dataset. During the actual biopsy, the position and orientation of the patient and the needle have to be known precisely and aligned with the pre-operative data.
Therefore two registrations have to be used for guiding the needle: the pre-operative data showing the lesion has to be registered with the patient. This can be done by attaching invariant markers to the patient (stereo-tactic frames) before data acquisition or by matching invariant patient features, such as the skull or bones.
The needle has to be registered with the patient. One possibility is to attach optical markers to the needle which can be tracked by a system of cameras or by X-ray fluoroscopy, or to use mechanical devices like passive robot arms that register the position of the needle at any moment. This technique requires highly specialized and costly 3-D imaging facilities that are typically only available at a few research sites. Despite the image guidance, a successful biopsy procedure still depends on the manual skills and judgement of the surgeon who is manipulating the needle.